1. Field of the Invention
The present invention relates generally to an image forming apparatus employing an electrophotographic reproduction method and, more particularly, to an image forming apparatus having a toner recycling assembly or mechanism for effecting toner recycling by conveying toner recovered by a cleaning unit to a developing unit.
2. Description of Related Art
Image forming apparatus are in wide practical use today wherein an electrostatic latent image formed on a support member such as, for example, a photosensitive drum is developed by a developing unit using powdered developer accommodated therein. A developing unit accommodating two-component developer consisting of toner and carrier, a developing unit accommodating monocomponent magnetic developer consisting of magnetic toner, and a developing unit accommodating monocomponent non-magnetic developer consisting of non-magnetic toner, and the like are known. In these developing units, the toner contained in the developer is consumed such that the toner adheres to an electrostatic latent image formed on the surface of the electrostatic latent image support member during development. However, part of the toner adhering to the electrostatic latent image is consumed without contributing to any image formation. More specifically, that portion of the toner which has adhered to the surface of the electrostatic latent image support member but has not been transferred to a transfer material such as, for example, a transfer paper or an intermediate transfer material is removed or recovered by the cleaning unit and is disposed of. In order to eliminate waste of the toner for the effective use thereof, various attempts have been made for toner recycling by conveying the toner recovered by the cleaning unit to the developing unit. Although such attempts greatly contribute to the elimination of waste of the toner, the following new problem occurs.
In general, the toner is surface-treated with a fluid material such as, for example, silica, thereby enhancing the fluidity of the toner. The toner recovered by the cleaning unit is, however, subjected to various stresses by contacting the transfer material or the like. Because of this, the fluid material on the surface of the toner tends to be separated therefrom or tends to be embedded therein, thereby reducing the fluidity of the toner. Accordingly, the toner recovered by the cleaning unit occasionally aggregates when being conveyed to the developing unit or inside the developing unit, or is accumulated without being sufficiently mixed with the developer in the developing unit. As a result, a noise such as "fogging" occurs on an image.